Speed up native AST materialization

[adamziel]

Summary

• reuse one WP_MySQL_Parser instance inside the SQLite driver and reset its token stream per query
• add reset_tokens() to the PHP parser polyfill and the Rust native parser
• restore native parser-node accessor fast paths in WP_MySQL_Native_Parser_Node, while keeping PHP child materialization for mutation
• fix the local native extension build helper for Nix/libclang bindgen by undefining __SSE2__ during binding generation

Stack

This is the top PR in the native MySQL lexer/parser stack. The stack is split so each GitHub diff shows one reviewable concern:

1. #384 Extract MySQL lexer and parser polyfills

   • trunk -> codex/native-parser-php-facade
   • extraction-only PHP refactor
   • moves the existing PHP lexer/parser implementations into polyfill classes
   • keeps public WP_MySQL_Lexer and WP_MySQL_Parser as thin PHP subclasses

2. #385 Add optional native parser routing

   • codex/native-parser-php-facade -> codex/native-parser-class-routing
   • adds fallback WP_MySQL_Native_* PHP classes
   • routes the public lexer/parser classes through native classes when the Rust extension provides them
   • adds the minimal PHP grammar-export bridge for the native parser

3. #386 Add lazy native parser node facade

   • codex/native-parser-class-routing -> codex/native-parser-node-facade
   • keeps WP_Parser_Node as the plain PHP tree node
   • adds WP_MySQL_Native_Parser_Node extends WP_Parser_Node for native-backed lazy AST nodes
   • keeps native AST handles and native accessor delegation out of the base node class

4. #381 Add lazy native AST facade

   • codex/native-parser-node-facade -> codex/native-lazy-ast-facade
   • implements the Rust lexer/parser extension and lazy native AST facade
   • makes the Rust extension instantiate WP_MySQL_Native_Parser_Node
   • adds native-extension CI coverage for the SQLite driver and WordPress PHPUnit tests
   • includes the local SQLite facade smoke benchmark

5. #387 Cache native grammar on parser grammar object

   • codex/native-lazy-ast-facade -> codex/native-parser-object-grammar-cache
   • restores the object-attached native grammar cache
   • adds only WP_Parser_Grammar::$native_grammar on the PHP side
   • removes the Rust content-hash cache that walked the whole exported grammar on every parser construction

6. This PR, #388 Speed up native AST materialization

   • codex/native-parser-object-grammar-cache -> codex/native-parser-bulk-materialization
   • optimizes native-to-PHP AST access after the grammar-cache performance restoration
   • reuses the SQLite driver's parser instance instead of constructing it per query

Why

The native lexer/parser itself is fast, but the PHP-facing path can lose that benefit if each query repeatedly rebuilds native parser state or forces full PHP AST materialization. On the current stack, #387 already removes the large grammar export/hash cost. This PR removes the remaining per-query parser construction churn and restores the native AST accessor path for descendant-heavy SQLite driver workloads.

Measurements

Environment: local PHP 8.2 via the native build helper, release Rust extension, current top of this PR.

Focused constructor/reset benchmark over 5000 unique SELECT queries:

Phase	Time
native tokenize	22.62 us/query
fresh native parser constructor only	2.31 us/query
reusable parser reset_tokens() only	0.32 us/query
reusable parser reset + parse + get_descendants()	157.06 us/query
constructor/reset ratio	7.3x

The previously reported ~622 us/query constructor cost does not reproduce on this stack because #387 already caches the native grammar on the PHP grammar object. Parser reuse still removes most of the remaining constructor overhead.

SQLite facade smoke workload:

Command:

TMP_TEST_NATIVE_QUERY_COUNT=250 ./tmp-test-native/run.sh

Workload	PHP fallback	Native extension	Speedup
250 generated queries, including 1 x 2000-row insert	4.060s	0.525s	7.73x

Testing

• cargo fmt --check
• git diff --check
• composer run check-cs
• composer run test from packages/mysql-on-sqlite
• php -d extension=packages/mysql-on-sqlite/ext/wp-mysql-parser/target/release/libwp_mysql_parser.so packages/mysql-on-sqlite/vendor/bin/phpunit -c packages/mysql-on-sqlite/phpunit.xml.dist
• TMP_TEST_NATIVE_QUERY_COUNT=250 ./tmp-test-native/run.sh